METHOD OF THE PREPARATION OF CdS OR CdSe POWDER FOR ELECTROPHOTOGRAPHY AND METHOD OF MAKING AN ELECTROPHOTOGRAPHIC PHOTOSENSITIVE PLATE BY USING THE POWDER

ABSTRACT

CdS or CdSe powders are treated by adding silver or copper as an activator, firing the mixture in the presence of CdCl2 or ZnO together with HC1, and after washing and drying the resultant powder, firing the dried powder in an atmosphere of S vapor. The powder thus produced is mixing with a bonding resin to form a photosensitive layer and an electrophotographic photoconductive plate is made therefrom.

United States Patent Hanada et al. 1 Mar. 7, 1972 [54] METHOD OF THEPREPARATION OF [56] ReIerences Cited CDS OR CDSE POWDER FORELECTROPIIOTOGRAPIIY AND STATES PATENTS METHOD OF MAKING AN 2,876,2023/1959 Busanovich et al ..252/50l ELECTROPHMOGRAPHIC 333123 5232;?."-""";;i ""3211? i PHOTOSENSITIVE PLATE BY USING i e ringer e THEPOWDER FOREIGN PATENTS OR APPLICATIONS [72] Inventors: Hiroshi lhnada,Yokohama-shi; Nobuo 863,004 3/1961 Great Britain ..252l50l Kitajima,Tokyo, both of Japan [73] Assignee: Canon Camera Kabushiki Knisha TokyoPrim Examiner-George Lesmes Japan Assistant Examiner-John R. MillerAttorneyWard, McElhannon, Brooks & Fitzpatrick [22] Filed: June 5, 1968[21] Appl. No.: 734,637 [57] ABSTRACT CdS or CdSe powders are treated byadding silver or copper as an activator, firing the mixture in thepresence of CdCl, or [30] ZnO together with I-ICl, and after washing anddrying the June 8, 1967 Japan ..42/36627 resultant powder, firing thedried powder in an atmosphere of S vapor. The powder thus produced ismixing with a bonding U-S. ..96/1-5, resin to form a photosensitivelayer and an electrophoto- 5 graphic photoconductive plate is madetherefrom.

4 Claims, 1 Drawing Figure METHOD OF THE PREPARATION OF CDS OR CDSEPOWDER FOR ELECTROPIIOTOGRAPHY AND METHOD OF MAKING ANELECTROPIIOTOGRAPHIC PHOTOSENSITIVE PLATE BY USING THE POWDER Thisinvention relates to a method of the preparation of CdS or CdSe powderfor electrophotography and a method of making an electrophotographicphotosensitive plate by using the powder.

It is well known that pure CdS or CdSe powder is activated with silveror copper to form a photoconductive material. However, the object of theprior art above is to produce a photoconductive material which ispredominantly used in the usual photoconductive apparatus, but thephotoconductive material thus obtained is not suitable forelectrophotography.

Heretofore, a photoconductive material has been directly considered tobe a suitable electrophotographic material. However, with respect to anelectrophotographic system utilizing a persistent internal polarization,the conventional relation as above that a photoconductive material isalways a suitable electrophotographic material is not established.Therefore, it is not appropriate to use a conventional photoconductivemember as an electrophotographic material.

The object of this invention is to provide a method of preparing CdS orCdSe powder suitable for the preparation of an electrophotographicphotoconductive plate used in a method of a persistent internalpolarization type.

Another object of this invention is to provide a method of making anelectrophotographic photoconductive plate by I using the CdS or CdSepowder obtained by the invention.

In the prior art, a photoconductive material was prepared by thefollowing three steps, i.e., (i) adding silver or copper as anactivating agent (the first firing step), (ii) adding a halogen as acoactivating agent (the second firing step), and (iii) firing in anatmosphere of sulfur vapor to decrease the dark current (the thirdfiring step), or by the above mentioned steps (i) and (ii) excluding thestep (iii) when zinc chloride is used as a flux.

According to the method of this invention, the step (ii) (introducing ahalogen) as mentioned above in the prior art is omitted and only the twosteps, that is, the first firing step for adding silver or copper andthe third firing step for treating with sulfur vapor, are employed toproduce CdS or CdSe powder suitable for an electrophotographic material.

According to the second method of this invention, the CdS or CdSe powderprepared by the first method of this invention as mentioned above ismixed with a binder resin and the resulting mixture is made into a layerof 50-100 y. thick between a support and an insulating film to form anelectrophotographic photosensitive plate. The attached drawingillustrates an embodiment of the photosensitive plate obtained by themethod of this invention.

With reference to the drawing, the photosensitive plate comprises asupport I, a photosensitive layer 2 which is formed by bonding the CdSor CdSe powder prepared by the first method of this invention with aresinous material such as, for example, synthetic resin, and aninsulating layer 3.

The final properties of CdS or cdSe powder obtained by the method ofthis invention are free from dispersion and the powder size is verysmall. Thus, the sharpness of the image is markedly improved and furtherwhen the powder thus obtained is used for a photoconductive plate, theresulting photoconductive plate gives an image of high contrast.Furthermore, the process for the preparation is simple as compared withthe prior art since the second step is omitted.

The following examples are set forth for purposes of illustration onlyand are not to be construed as limitations on the present inventionexcept as set forth in the appended claims.

Example 1 Pure cadmium sulfide l g., cadmium chloride l0 g., ammoniumchloride 1 g., cupric chloride 0.03 g., and deionized water 250 cc. arethoroughly mixed, dried, placed in a quartz test tube, fired in anatmosphere of nitrogen for 30 minutes at 600 C., washed with water,dried, screened by a 325 mesh screen, placed together with 0.2 g. ofsulfur powder in a quartz test tube, and fired in an atmosphere ofnitrogen at 500C. for 10 minutes and then under vacuum for further 10minutes.

Example 2 Example 3 By using cadmium selenide powder in place of cadmiumsulfide, the procedures in Example 1 or Example 2 are repeated.

Example 4 Epoxy resin Epikote 815 (trademark for liquid epoxy resinhaving a molecular weight about 350, viscosity of five through ninepoises at 25 C.) containing about 12 percent by weight of an amineseries hardener manufactured by Anchor Chemical Co. is added as abonding agent to CdS powder obtained in Example I or Example 2 at anamount of about 15 percent by weight on the basis of the CdS powder,sufficiently mixed, and the resulting mixture is transferred ontoaluminum foil and then rapidly spread and leveled off to a thickness ofabout u. The leveling is carried out by using a frame of thin metalplate as a spacer, covering the above-mentioned mixture with a Mylar(trademark) for polyethylene terephthalate manufactured by Du Pontinsulating film of about 25 a in thickness, and leveling off the mixturethrough the Mylar film with an edge of a metal bar having a wedgelikecross section to form a thin layer.

Example 5 The mixture as used in Example 4 above is put on a Mylar filmplaced on a flat plate and directly leveled off to form a photosensitivelayer. Then, the resulting whole matter is turned upside down and placedon an appropriate support.

Example 6 ln Example 4 above, an insulating film such as Mylar is usedin place of the metal foil.

The photosensitive plate obtained in the above Examples is used to forman electrostatic latent image. By comparing the contrast of theelectrostatic latent images thus formed, the quality of thephotosensitive plate and the material used for preparing thephotosensitive plate is finally determined.

The photosensitive plate as mentioned above is positively charged bycorona discharging in a light or dark place, exposed to an imageirradiation at an intensity of i0 Iux. sec, and similarly negativelycharged by corona discharging. Finally, the whole photosensitive plateis exposed to light. These steps may be considered in view of physicalpoint of view as follows. The positive surface potential formed by theinitial charging induces a polarization in the photosensitive plate.This polarization persists at a dark portion of the image when the imageirradiation is effected simultaneously with the negative charging.Therefore, the charge at the light portion is changed to negative chargewhile the negative charging does not proceed at a dark portion due torepulsion of the polarity and a slightly neutralized state appears.Then, when the persistent internal polarization disappears by the finalwhole irradiation, electrostatic latent images of negative potential andnearly neutral potential are produced on the photosensitive plate.

By using the photosensitive plate having the structure as mentionedabove, the electrostatic contrast of the electrostatic latent imageformed by using a conventional photoconductive member is compared withthat formed by using the material obtained by this invention. The resultis shown in Table 1 below.

No'rE.-(Unit: volt).

The above data clearly indicates that the photosensitive.

plate made of the material prepared by the method of this inventioncomprising two steps including a sulfur treating step excluding thesecond firing step in the conventional process which has been consideredas an indispensable treatment for improving the property ofphotoconductive member shows an excellent performance.

What is claimed is'.

1. A method for preparing an electrophotographic photoconductive platewhich consists essentially of adding silver or copper as an activator toCdS or CdSe powder, firing the resulting mixture in the presence of atleast one member selected from the group consisting of (a) cadmiumchloride and (b) zinc oxide together with hydrochloric acid, washing theresultant powder with water, drying said powder, firing the dried powderin an atmosphere of sulfur vapor, mixing a bonding resin with the CdS orCdSe powder and placing the resulting mixture as a photosensitive layerof 50-100 p in thickness between a support and an insulating film.

2. A method according to claim 1 wherein the first firing is carried outat a temperature of 600 C. for 20-30 minutes and the second firing iscarried out at a temperature of 500 C. for 10 minutes in an atmosphereof sulfur vapor and thereafter under vacuum for 10 minutes.

3. A method according to claim 1 wherein the bonding resin comprises anepoxy resin.

4. A method according to claim 3 wherein the insulating film comprisespolyethylene terephthalate.

2. A method according to claim 1 wherein the first firing is carried outat a temperature of 600* C. for 20-30 minutes and the second firing iscarried out at a temperature of 500* C. for 10 minutes in an atmosphereof sulfur vapor and thereafter under vacuum for 10 minutes.
 3. A methodaccording to claim 1 wherein the bonding resin comprises an epoxy resin.4. A method according to claim 3 wherein the insulating film comprisespolyethylene terephthalate.